This invention relates to a driving device, particularly for driving the wheels of a motor vehicle such as excavators and wheel loaders.
In power shift transmissions, such as used in industrial vehicles, it is known to provide an auxiliary release device by which the drive train of the vehicle is interrupted thus making it possible to tow a vehicle that has broken down.
The Applicant""s DE 44 08 472 describes a driving device which is provided with an input, a mechanical gear rear-mounted thereon and two hydraulically shiftable friction couplings and friction brakes through which the input can be connected with the gear and which perform the functions of a parking brake. Friction coupling and friction brake are connected via control-pressure lines with an auxiliary release device which has an adjustable accumulator piston and gear shift pistons interacting therewith so that when the accumulator piston is actuated, the gear shift pistons supply the contents of the accumulator piston via the control-pressure lines of the friction coupling and of the friction brake in the sense of a separation.
The device can have a compensation cylinder where is situated a compensation piston prestressed by a spring device and connected with the contents of the accumulator piston so that in the hydraulic system of the auxiliary release device an even pressure always prevails and pressure changes due to temperature oscillations are compensated without problem.
The problem on which this invention is based is further to simplify the construction of such a driving device with which a vehicle in broken down state can be towed without problem and thereby to reduce the cost of production.